Aspirators for producing vacuum using the venturi effect

ABSTRACT

A Venturi device for producing vacuum from fluids in an engine system has a body defining a Venturi gap separating apart an outlet end of a converging motive section and an inlet end of a diverging discharge section by a lineal distance, and a suction port in fluid communication with the Venturi gap. The converging motive section and the diverging discharge section both gradually, continuously taper toward the Venturi gap, the converging motive section defines a circular-shaped motive inlet and an elliptical- or polygonal-shaped motive outlet, the diverging discharge section defines an elliptical- or polygonal-shaped discharge inlet, and an inner passageway of the converging motive section transitions as a hyperbolic function from the motive inlet to the elliptical- or polygonal-shaped motive outlet.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/294,727, filed Jun. 3, 2014, which claims the benefit of U.S.Provisional Application No. 61/833,746, filed Jun. 11, 2013.

TECHNICAL FIELD

This application relates to aspirators for producing vacuum using theVenturi effect, more particularly to such aspirators having increasedsuction flow by increasing the perimeter of the inner passageway at themotive outlet end and the discharge inlet end for a maximum motive flowrate selected by a customer.

BACKGROUND

Engines, for example vehicle engines, are being downsized and boosted,which is reducing the available vacuum from the engine. This vacuum hasmany potential uses, including use by the vehicle brake booster.

One solution to this vacuum shortfall is to install a vacuum pump.Vacuum pumps, however, have a significant cost and weight penalty to theengine, their electric power consumption can require additionalalternator capacity, and their inefficiency can hinder fuel economyimprovement actions.

Another solution is aspirators that generate vacuum by creating anengine air flow path that is parallel to the throttle, referred to as anintake leak. This leak flow passes through a Venturi that generates asuction vacuum. The problem with the presently available aspirators isthat they are limited in the amount of vacuum mass flow rate they cangenerate, and by the amount of engine air they consume, for example,aspirators having a circular cross-section at the motive outlet end andthe discharge inlet end as shown in FIG. 3 and as disclosed in U.S.Application Publication 2006/0016477 and U.S. Application Publication2013/0213510.

A need exists for improved designs that generate increased vacuumpressure and increased suction mass flow rate while decreasing theconsumption of engine air.

SUMMARY

Aspirators are disclosed herein that generate increased vacuum pressureand increased suction mass flow rates while decreasing the consumptionof engine air. Such aspirators include a body defining a Venturi gapbetween an outlet end of a converging motive section and an inlet end ofa diverging discharge section. The converging motive section has anelliptical- or polygonal-shaped internal cross-section motive outlet andthe diverging discharge section has an elliptical- or polygonal-shapedinternal cross-section discharge inlet, and the converging motivesection and the diverging discharge section, together, define an innerpassageway formed by hyperboloid curves connecting a motive inlet to theelliptical or polygonal-shaped motive outlet or the elliptical orpolygonal-shaped discharge inlet to a discharge outlet. In oneembodiment, at least one of the motive inlet or the discharge outlet hasa circular internal cross-section.

The aspirators may include a suction port defining a void in fluidcommunication with the Venturi gap. Here, a first portion of the bodythat defines the outlet end of the converging motive section and asecond portion of the body that defines the inlet end of the divergingdischarge section lay on the surface of the void and the void extendsdownward around the sides of both the first body portion and the secondbody portion. In one embodiment, the exterior profile of both the firstportion and the second portion of the body generally match the internalcross-section of the inlet end and the outlet end, respectively.

In one aspect, the aspirators are constructed with the elliptical- orpolygonal-shaped internal cross-section of the outlet end of theconverging motive section having a ratio of the major axis to the minoraxis of about 2 to about 4, and the elliptical- or polygonal-shapedinternal cross-section of the inlet end of the diverging dischargesection being offset, relative to the elliptical- or polygonal-shapedinternal cross-section of the outlet end of the converging motivesection, by the ratio of the difference of the discharge inlet area andthe motive outlet area to the peak motive mass flow rate ((dischargeinlet area−motive outlet area)/peak motive flow rate) times a constant,where the ratio is greater than 0.28.

In one embodiment, the Venturi gap is proportional to the (motive massflow rate)^(n), wherein n is 0.25 to 0.8, and the offset between themotive outlet and the discharge inlet is proportional to the (motivemass flow rate)^(n), where n is 0.25 to 0.8, and the elliptical- orpolygonal-shaped internal cross-section of the outlet end has aneccentricity of between 0 to, and including 1. In one embodiment, n forthe Venturi gap and n for the offset may both be 0.4 to 0.6.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, longitudinal cross-sectional plan view of oneembodiment of an aspirator.

FIG. 2 is a top plan view, in cross-section, of the aspirator of FIG. 1.

FIG. 3 is a side, cross-sectional perspective view taken along a planeparallel to the central longitudinal axis B at the junction of thesuction port in the aspirator in a prior art aspirator having circulartransverse cross-sections in the motive section and the dischargesection.

FIG. 4A is a side, cross-sectional perspective view taken along a planeparallel to the central longitudinal axis B at the junction of thesuction port in the aspirator of FIG. 2.

FIG. 4B is a representation of the volume of the Venturi gap in FIG. 4A.

FIG. 5A is a side, cross-sectional perspective view taken along a planeparallel to the central longitudinal axis B at the junction of thesuction port in another embodiment of an aspirator.

FIG. 5B is a representation of the volume of the Venturi gap in FIG. 5A.

FIG. 6 is a plan view looking into the aspirator from the aspiratoroutlet showing the offset between the motive outlet end and thedischarge inlet end.

FIG. 7 is a model of the internal passageway within the motive sectionof the aspirator.

FIG. 8 is a graphical representation comparing the aspirator suctionflow rates of a hyperboloid ellipse aspirator disclosed herein against aconical circular aspirator (prior art) at different selected manifoldvacuum values.

FIG. 9 is a graphical representation comparing the aspirator vacuum of ahyperboloid ellipse aspirator disclosed herein against a conicalcircular aspirator (prior art) as the manifold vacuum increases.

FIG. 10 is a graphical representation comparing the time to evacuate acanister by a hyperboloid ellipse aspirator disclosed herein against aconical circular aspirator (prior art) as the manifold vacuum increases.

DETAILED DESCRIPTION

The following detailed description will illustrate the generalprinciples of the invention, examples of which are additionallyillustrated in the accompanying drawings. In the drawings, likereference numbers indicate identical or functionally similar elements.

As used herein “fluid” means any liquid, suspension, colloid, gas,plasma, or combinations thereof.

FIGS. 1 and 2 illustrate different views of an aspirator 100. Theaspirator 100 may be used in an engine, for example, in a vehicle'sengine to provide vacuum to a device. In FIG. 1 the aspirator 100 isconnected to a device requiring vacuum 102, and the aspirator 100creates vacuum for said device 102 by the flow of air through apassageway 104, extending generally the length of the aspirator,designed to create the Venturi effect. Aspirator 100 includes a body 106defining passageway 104 and having three or more ports that areconnectable to an engine or components connected thereto. The portsinclude: (1) a motive port 108, which may be connected to a source ofclean air, e.g., from the engine intake air cleaner, that is positionedupstream of a throttle; (2) a suction port 110, which can connect via anoptional check valve 111 to the device requiring vacuum 102; (3) anaspirator outlet 112, which is connected to an engine intake manifolddownstream of the throttle of the engine; and, optionally, (4) a bypassport 114. Each of the respective ports 108, 110, 112, and 114 mayinclude a connector feature 117 on the outer surface thereof forconnecting the respective port to a hose or other component in theengine.

Check valve 111 is preferably arranged to prevent fluid from flowingfrom the suction port 110 to the application device 102. In oneembodiment, the device requiring vacuum 102 is a vehicle brake boostdevice, positive crankcase ventilation (PCV) device, or fuel purgedevice. In another embodiment, the device requiring vacuum 102 is ahydraulic valve. The bypass port 114 may be connected to the devicerequiring vacuum 102 and, optionally, may include a check valve 120 inthe fluid flow path 122 therebetween. Check valve 120 is preferablyarranged to control the flow of fluid to or from the bypass port 114 tothe application device 102.

Referring now to FIGS. 2 and 3, the aspirator 100 is generally a“T-shaped” aspirator defining an inner passageway along a centrallongitudinal axis B bisected by the suction port 110. The innerpassageway 104 includes a first tapering portion 128 (also referred toherein as the motive cone) in the motive section 116 of the body 106coupled to a second tapering portion 129 (also referred to herein as thedischarge cone) in the discharge section 146 of the body 106. Here, thefirst tapering portion 128 and the second tapering portion 129 arealigned end to end having the motive outlet end 132 facing the dischargeinlet end 134 and defining a Venturi gap 152 therebetween, which definesa fluid junction placing the suction port 110 in fluid communicationwith both the motive section 116 and the discharge section 146 of theinner passageway 104. The Venturi gap 152 as used herein means thelineal distance between the motive outlet end 132 and the dischargeinlet end 134.

When an aspirator, such as aspirator 100, is for use in a vehicleengine, the vehicle manufacturer typically selects the size of both themotive port 108 and aspirator outlet 112 based on the tubing/hose sizeavailable for connection of the aspirator to the engine or componentsthereof. Additionally, the vehicle manufacturer typically selects themaximum motive flow rate available for use in the aspirator, which inturn will dictate the area of the interior opening defined at the motiveoutlet end 132, i.e., the motive outlet 133. Accordingly, the vehiclemanufacturer's selected parameters for the particular engine dictate theratio of the motive outlet 133 to the aspirator outlet 112. Workingwithin these constraints, the disclosed aspirators 100 significantlyreduce the compromise between the desire to produce high suction flowrates at low (5 kPa to 30 kPa) source/discharge pressures and increaseddepth of vacuum at higher (30 kPa to 60 kPa) source discharge pressures.This reduction in the compromise is accomplished by changing theconfiguration for the motive outlet 133 and the discharge inlet 135(defined by the discharge inlet end 134) to increase the perimeter ofthe inner passageway 104 at the motive outlet end 132 and the dischargeinlet end 134, such as presented in FIGS. 5 and 6.

As illustrated in FIGS. 5A-5B and 6, at least the interior surface ofthe motive outlet end 132 (the motive outlet 135) and the interiorsurface of the discharge inlet end 134 (the discharge inlet 135) areellipse-shaped, but may alternately have a polygonal form. The interiorof the inner passageway 104 extending away from the motive outlet end132 and away from the discharge inlet end 134, in opposite directions,from the Venturi gap 152, may be constructed to have the same generalshape. FIG. 7 illustrates one embodiment of the shape of the internalpassageway within the motive section of the aspirator, but equally, ifrotated 180 degrees illustrates the internal passageway within thedischarge section. The internal passageway in FIG. 7 begins at themotive inlet end 130 as a circular opening having an area A₁ andgradually, continuously transitions, a hyperbolic function, to anellipse opening at the motive outlet 135 that has an area A₂, which issmaller than A₁. The circular opening at the motive inlet end 130 isconnected to the ellipse-shaped motive outlet 135 by hyperbola lines 170that provide the advantage of flow lines at the motive outlet end 132being parallel to one another. The motive inlet end 130 and thedischarge outlet end 136 may also define ellipse-shaped or some otherpolygonal form openings at some point prior thereto and transition fromsaid shapes to a circular cross-section to form a hose connectingportion, for example similar to hose-connecting portion 119, havingconnector features 117 on the exterior thereof.

To form the “T” shape of the aspirator 100 the suction port 110 has acentral longitudinal axis C generally perpendicular to the body'scentral longitudinal axis B. The optional bypass port 114 may likewisehave a central longitudinal axis D that is generally perpendicular tothe body's central longitudinal axis B. As illustrated in FIG. 1, thebypass port 114 may intersect the second tapering section 129 adjacentto, but downstream of the discharge outlet end 136. The body 106 maythereafter, i.e., downstream of this intersection of the bypass port,continue with a cylindrically uniform inner diameter until it terminatesat the aspirator outlet 112. In another embodiment (not shown), thebypass port 114 and/or the suction port 110, rather than beingperpendicular, may be canted relative to axis B and/or to one another.In the embodiment of FIG. 2, the suction port 110 and the bypass port114 are aligned with one another and have the same orientation relativeto the body's central longitudinal axis B. In another embodiment, notshown, the suction port 110 and the bypass port 114 may be offset fromone another and can be positioned relative to components within theengine that they will connect to for ease of connection.

The suction port 110 includes a suction inlet 138 and a suction outlet,which is the discharge inlet 134, and similarly to the first taperingsection 128, may gradually, continuously taper as a cone or according toa hyperbolic function along its length from the larger dimensionedsuction inlet 138 to a smaller dimensioned suction outlet 134. Thebypass port 114, when present, may also gradually, continuously taper asa cone or according to a hyperbolic function along its length, inparticular from a smaller dimensioned end 162 to a larger dimensionedend 160. Depending upon the attachment of the aspirator into a system,the bypass port 114 may operate with the larger dimensioned end 160 asthe inlet and the smaller dimensioned end 162 as the outlet or viceversa.

As best seen in FIGS. 2 and 5, at the motive outlet end 132 of the firsttapering portion 128, juxtaposed to the second tapering portion 129, thesuction port 110 includes an enlarged region defining a void 150 influid communication with Venturi gap 152 or conversely the Venturi gap152 may be considered part of void 150. The fluid junction of thesuction port 110 with inner passageway 104 is generally centeredrelative to the Venturi gap 152 and the void 150 is generally alignedwith the suction port's central longitudinal axis C and transitions thefirst tapering portion 128 into the second tapering portion 129. Thevoid 150 may be shaped as parallelepiped whose length is similar to thesuction port's interior cross-section dimension(s), but whose bottom isan arcuate projection projecting downward away from the suction port110. In a cross-section taken transverse to the body's centrallongitudinal axis B along the suction port's central longitudinal axisC, the void is seen to be generally U-shaped around and/or over thedischarge inlet end 134 and the motive outlet end 132 as best understoodby viewing FIGS. 2, 4A, and 5A in combination. As seen in FIGS. 2 and5A, the suction port extends downward around the sides of the motiveoutlet end 132 and the sides of the discharge inlet end 134 and definesthe void 150 between all sides thereof. As seen in FIG. 5A, the exteriorprofile of the motive outlet end 132 and the discharge inlet end 134both generally match their respective internal shapes.

In aspirator 100, the flow of motive air through the first taperingportion 128 increases its speed, but creates low static pressure in thevoid 150. This low static pressure draws air from the suction port 110into the Venturi gap 152 and into the discharge section 146 through thedischarge inlet (suction outlet) 134.

The aspirator 100 may be operated to meet the following geometricratios:

Representative Symbol Ratio A′ suction inlet area/suction outlet area B′motive inlet area/motive outlet area C′ discharge outlet area/dischargeinlet area

There are also performance ratios as follows:

Representative Symbol Ratio F suction mass flow rate/motive mass flowrate G suction vacuum pressure/discharge vacuum pressure

To maximize the ratio F for the hyperbolical flow passageways disclosedherein, the ratio A′ should be between 3 and 12, and the ratio B′ shouldbe greater than 4, and the ratio C′ should be greater than 4.

To maximize the ratio G for hyperbolical flow passageways, the ratio A′should be between 3 and 12, and the ratio B′ should be greater than 4,and the ratio C′ should be greater than 4.

In the prior art of FIG. 3, the outlet end of the motive cone and theinlet end of the discharge cone each have circular internalcross-sections and circular exterior profiles and thereby define aVenturi gap that is a frustum having a circular outer periphery. Fromthis drawing, one of the limitations to suction flow is illustrated—thearea at the fluid junction of the suction port to the motive cone andthe discharge cone.

In a desire to increase the flow rate of air from the suction port intothe Venturi gap 152 of the aspirators disclosed herein, the area of theVenturi gap is increased by increasing the perimeter of the outlet end132 and the inlet end 134 without increasing the overall inner dimensionof the first tapering section 128 and the second tapering section 129(preferably with no increase in the mass flow rate). In particular,motive outlet end 132 and discharge inlet end 134 are changed from beingcircular to being non-circular as described above. There are an infinitenumber of possible shapes that are not circular, each with a perimeterand a cross sectional area. These include polygons, or straight-linesegments connected to each other, non-circular curves, and even fractalcurves. To minimize cost a curve is simpler and easy to manufacture andinspect, and has a desirable perimeter length.

FIGS. 4A-AB and 5A-5B illustrate embodiments with improved fluidjunctions where the suction port 110 meets the motive outlet end 132 andthe discharge inlet end 134. The smallest area of the flow path from thesuction port 110 to the Venturi gap 152 is the frustum defined betweenthe motive outlet end 132 and the discharge inlet end 134, see FIGS. 4Band 5B. In FIGS. 4A and 4B, the outlet end 132 of the motive cone 128and the inlet end 134 of the discharge cone 129 each have inner andouter elliptical perimeters and thereby define a Venturi gap 152 that isa frustum having an elliptical outer periphery. In FIGS. 5A and 5B, theoutlet end 132 of the motive cone 128 and the inlet end 134 of thedischarge cone 129 each have inner and outer generallyrectangular-shaped perimeters (with rounded corners) and thereby definea Venturi gap 152 that is a frustum having a generallyrectangular-shaped outer periphery. While the embodiments in the figureshave the same perimeter for the outlet end 132 and the inlet end 134,i.e., both are elliptical or both are generally rectangular, the outletend 132 and the inlet end 134 may have differently shaped perimeters,i.e., one may be elliptical while the other is generally rectangular.Additionally, the motive outlet end 132 and the discharge inlet end 134may terminate with a rounded chamfer to improve the directionality ofthe flow of the fluid from the suction port 110 in to the dischargeinlet end 134.

Additionally, as seen most clearly in FIG. 6, but is also seen in thefrustums of FIGS. 4B and 5B, the outlet end 132 of the motive cone 128for each embodiment is dimensionally smaller than the inlet end 134 ofthe discharge cone 129. This difference in dimension is identified asoffset 140. In FIG. 4B, for example, the offset is seen in that thelength of the major axis Y of the motive outlet end 132 is less than thelength of the major axis Y′ of the discharge inlet end 134 and may alsohave a length of the minor axis X of the motive outlet end 132 that isless than the length of the minor axis X′ of the discharge inlet end134.

In any of the elliptical- or polygonal-shaped embodiments, theelliptical- or polygonal-shaped internal cross-section of the motiveoutlet end of the converging motive section has a ratio of the majoraxis to the minor axis of about 2 to about 4, and the elliptical- orpolygonal-shaped internal cross-section of the inlet end of thediverging discharge section is offset, relative to the elliptical- orpolygonal-shaped internal cross-section of the outlet end of theconverging motive section, by the ratio of the difference of thedischarge inlet area and the motive outlet area to the peak motive flowrate, which is then multiplied by a constant k₁ to have a unitless ratioof greater than 0.28.

Offset ratio=(discharge inlet area−motive outlet area)/peak motive flowrate*k ₁   (V)

where k₁ is:

k ₁ =c at the motive outlet end*D _(fluid) at the motive outlet end;  (VI)

and c is the speed of sound and D_(fluid) is the density of the fluid(typically air).

In any of the elliptical- or polygonal-shaped embodiments, the Venturigap between the motive outlet end and the discharge inlet end has a gapratio defined as the area of the Venturi gap divided by the motive flowtimes a constant k₂ (to have a unitless ratio).

gap ratio=area of the Venturi gap/motive flow rate*k ₂   (VII)

where k₂ is:

k ₂ =c at the motive outlet end*D _(fluid) at the motive outletend;  (VIII)

and c and D_(fluid) are as defined above. Here, the gap ratio is greaterthan 4.7.

In one embodiment, the elliptical- or polygonal-shaped internalcross-section of the motive outlet end 132 has an eccentricity ofbetween 0 to, and including 1. In another embodiment, the elliptical- orpolygonal-shaped internal cross-section of the outlet end has aneccentricity of between about 0.4 to, and including about 0.97.

Referring again to FIGS. 4A and 4B, the outlet end 132 and the inlet end134 are elliptical in profile thereby having a major axis (Y) and aminor axis (X). The equation of an ellipse can be defined as;X²/B²+Y²/A²=1². Where A is the distance from the origin to the ellipsealong the major axis Y and B is the distance from the origin to theellipse along the minor axis X. The area of an ellipse is:

Area of an ellipse=π×A×B.  (I)

The perimeter of an ellipse is not given by a simple exact equation.Instead a series equation provides an acceptable approximation;

Perimeter of an ellipse=π×(A+B)×(1+h ²/4+h ⁴/64+h ⁶/256 . . . )  (II)

where h is:

Variable h=(A−B)/(A+B).  (III)

We can further define a term, eccentricity, which is a term that relatesthe length of the two axes. It is defined as:

Variable e=(A ² −B ²)^(1/2) /A.  (IV)

Given a selected motive flow for the aspirator design being chosen to beequivalent for calculations where the radius of the prior art circularaspirator is 1 mm, the area is of 3.14 mm² with a perimeter of 6.28 mm.The ratio of perimeter to area is mathematically equal to 2 for acircular internal cross-section for the motive outlet end and thedischarge inlet end.

For an ellipse of a given eccentricity we can compute the area,perimeter and the ratio of perimeter to cross sectional area in thedisclosed embodiments. If we limit the area to be equal to that of acircle of radius of 1 mm, the calculated results are as follows;

TABLE 1 ellipse ratio perimeter A B area perimeter to area e (mm) (mm) h(mm² ₎ (mm) (mm⁻¹) 0.000 1.000 1.000 0.000 3.142 6.283 2.000 0.431 1.0530.950 0.051 3.143 6.297 2.004 0.586 1.111 0.900 0.105 3.141 6.335 2.0170.691 1.176 0.850 0.161 3.140 6.406 2.040 0.768 1.250 0.800 0.220 3.1426.518 2.075 0.827 1.333 0.750 0.280 3.141 6.673 2.125 0.872 1.429 0.7000.342 3.143 6.886 2.191 0.906 1.538 0.650 0.406 3.141 7.160 2.280 0.9331.667 0.600 0.471 3.142 7.522 2.394 0.953 1.818 0.550 0.535 3.141 7.9832.541 0.968 2.000 0.500 0.600 3.142 8.578 2.731 0.979 2.222 0.450 0.6633.141 9.345 2.975 0.987 2.500 0.400 0.724 3.142 10.349 3.294 0.992 2.8570.350 0.782 3.141 11.682 3.719 0.996 3.333 0.300 0.835 3.141 13.5044.299 0.998 4.000 0.250 0.882 3.142 16.102 5.125 0.999 5.000 0.200 0.9233.142 20.041 6.379 1.000 6.667 0.150 0.956 3.142 26.653 8.483 1.00010.000 0.100 0.980 3.142 39.919 12.707 1.000 20.000 0.050 0.995 3.14279.783 25.396

So, by changing the eccentricity, the perimeter can be increased whileholding the cross sectional area fixed. This increase in perimeterprovides the advantage of increasing the intersection area at thejunction between the suction port, the motive cone, and the dischargecone, resulting in an increase in the suction port flow rate.

Referring now to FIGS. 5A and 5B, the motive outlet end 132 and thedischarge inlet end 134 are generally rectangular in profile therebyhaving a length and a width and hence two axes, a major axis A and aminor axis B. As illustrated, the aspirator's generally rectangularprofile for the outlet end 132 and inlet end 134 include semicircularends corresponding to the width of the rectangular portion. Theorientation of the profile of the outlet and inlet ends 132, 134 shouldnot be construed to be limited thereto. The area of this rectangle isequal to the sum of the areas of the two end semicircles plus the areaof the straight section in between the semicircles. The perimeter of therectangle is the lengths of the two sides plus the lengths of thesemicircular ends. We can calculate the following;

TABLE 2 Rectangle ratio of perimeter A (mm) B (mm) area (mm²) perimeter(mm) to area (mm⁻¹) 1.000 1.000 3.142 6.283 2.000 1.272 0.950 3.1426.614 2.105 1.563 0.900 3.142 6.981 2.222 1.876 0.850 3.142 7.392 2.3532.214 0.800 3.142 7.854 2.500 2.583 0.750 3.142 8.378 2.667 2.989 0.7003.142 8.976 2.857 3.441 0.650 3.142 9.666 3.077 3.951 0.600 3.142 10.4723.333 4.534 0.550 3.142 11.424 3.636 5.212 0.500 3.142 12.566 4.0006.018 0.450 3.142 13.963 4.444 6.997 0.400 3.142 15.708 5.000 8.2260.350 3.142 17.952 5.714 9.829 0.300 3.142 20.944 6.667 12.031 0.2503.142 25.133 8.000 15.280 0.200 3.142 31.416 10.000 20.623 0.150 3.14241.888 13.333 31.202 0.100 3.142 62.832 20.000 62.725 0.050 3.142125.664 40.000

Changing from a circular cross section to a generally rectangular onewith the same area results in an increase in the ratio of perimeter toarea similarly to the elliptical profile described above. This increasein perimeter will again provide the advantage of increasing theintersection area between the Venturi gap and the suction port,resulting in an increase in suction port flow.

Another way to increase suction flow would be to lengthen the distancebetween the outlet end 132 of the motive cone 128 and the inlet end 134of the discharge cone 129. As the motive flow travels through theVenturi gap it mixes with suction air. This combined flow has the effectof increasing the static pressure towards the discharge end of theVenturi. Lengthening this distance offers diminishing returns, andbecause the motive flow is largely unconstrained in the Venturi, offersthe risk of turbulence and flow disturbance, which would reduce thevelocity and increase static pressure. Accordingly, the increase inperimeter described above is preferred over lengthening the distance,but the two could be combined to avoid the diminishing returns.

The aspirators disclosed herein may be molded as a monolithic body. Inone embodiment, the aspirators are formed by injection molding.

In one embodiment, the Venturi gap 152 is a lineal distance proportionalto the (motive mass flow rate)^(n), wherein n is 0.25 to 0.8, and theoffset between the motive outlet and the discharge inlet is alsoproportional to the (motive mass flow rate)^(n), where n is 0.25 to 0.8,and the elliptical- or polygonal-shaped internal cross-section of theoutlet end has an eccentricity of between 0 to, and including 1, or morepreferably between about 0.4 to, and including about 0.97. When theaspirator is included in a system having a device requiring higheramounts of vacuum, n for the Venturi gap and n for the offset may bothbe 0.4 to 0.6. In one embodiment, n for the Venturi gap and n for theoffset are both 0.5 and the eccentricity is between about 0.4 to, andincluding 0.97.

In operation, for example when the aspirator is connected into anengine, engine air, i.e. filtered air, can be connected to enter theaspirator at the motive port. Air exiting the aspirator at the dischargeport can be connected to the engine air at a point where the pressure islower than that of the motive port. The motion of the air from themotive to discharge port draws the air down the motive cone, which canbe a straight cone or a hyperbolic profile as described above. Thereduction in area causes the velocity of the air to increase. Becausethis is an enclosed space the laws of fluid mechanics state that thestatic pressure must decrease when the fluid velocity increases. Theminimum cross-sectional area of the motive cone abuts the Venturi gap.As air continues to travel to the discharge port it travels through thedischarge cone, which is either a straight cone or a hyperbolic profile.Optionally, the discharge region can continue as a straight orhyperbolic profile cone until it joins the discharge port, or it cantransition to a simple cylindrical or tapered passage. The minimumcross-sectional area end of the discharge cone is larger than that ofthe minimum cross section area end of the motive cone. The larger areais to provide area for the flow of air from the suction port. Thischange in area down the discharge cone slows the air velocity downagain, with a subsequent increase in its static pressure.

The Venturi gap connects to the suction port, which exposes air in thesuction port/passage to the same low static pressure that exists in theair passing at high velocity between the motive and discharge cones. Thepressure created here can be lower than the pressure at the dischargeport, which is known already to be lower than that at the motive port.This low pressure may be used for a variety of applications on avehicle, such as for evacuating a vehicle brake boost canister, as isknown to those skilled in the art. Under some circumstances, primarilywhen the gasoline engine is lightly loaded, the pressure at thedischarge port is low enough to quickly lower the pressure at theapplication device. Since the area of the connection between thedischarge cone or passage and the bypass passage is quite large relativeto the connection between the suction passage and the Venturi gap, thisoptional connection can assist in evacuation of the application deviceinitially.

For a comparison study a 3 gps aspirator having an elliptical motiveoutlet and an elliptical discharge inlet at the Venturi gap and ahyperboloid internal profile in the motive and discharge sections,(referred to as the “hyperboloid ellipse aspirator”) as illustrated inFIG. 7, was operated under conditions of 10 kPa manifold vacuum, 15 kPamanifold vacuum, and 20 kPa manifold vacuum with increasing brake boostcanister vacuum and compared to a 3 gps conical circular aspirator underthe same conditions. A conical circular aspirator is one that has acircular motive outlet and a circular discharge inlet and a conicalinternal profile in the motive and discharge sections. As evidenced bythe data presented in FIG. 8, the hyperboloid ellipse aspirator provideda synergistic effect of the hyperboloid internal profile with theellipse-shaped openings that exceeded the results of the conicalcircular aspirator. At 10 kPa, 15 kPa, and 20 kPa manifold pressure, thehyperboloid ellipse aspirator provided higher suction flow rates over anincreasing range of brake boost canister vacuum from 12 kPa to about 67kPa. Interestingly, at 15 kPa manifold pressure the hyperboloid ellipseaspirator performed generally similar to the conical circular aspiratorwhen it was at 20 kPa manifold pressure, evidencing unexpected, superiorperformance.

Referring now to FIGS. 9 and 10, the same aspirators compared for FIG. 8were compared with respect to the ultimate vacuum the aspirator couldgenerate and the time needed for the aspirator to evacuate a canister tocreate vacuum. For the tests, the aspirator outlet 112 was in fluidcommunication with an intake manifold of the engine, the suction portwas in fluid communication with a vehicle brake boost canister, and themotive inlet was connected to a source of clean air. As shown in thegraph of FIG. 9, the hyperboloid ellipse aspirator disclosed hereinprovides a deeper vacuum compared to the conical circular aspiratorunder the same operating conditions, i.e., at 10, 15, and 20 kPA ofmanifold vacuum the hyperboloid ellipse aspirator had an ultimate vacuumthat was greater by at least 5 kPa. Additionally, as seen in FIG. 10,the hyperboloid ellipse aspirator was superior in evacuating a brakeboost canister compared to the conical circular aspirator. At a manifoldvacuum pressure of 10 kPa, the hyperboloid ellipse aspirator was justunder 4.5 seconds faster at evacuating the canister. At 15 kPa and 20kPa of manifold vacuum the hyperboloid ellipse aspirator was about 2seconds faster. Faster evacuation times at lower manifold vacuumprovides for faster reaction time and improved performance. But, as seenin these graphs, not only does the aspirator with the hyperboloidelliptical profile have faster evacuation time, it also provides adeeper vacuum at manifold vacuums of 10, 15, and 20 kPa. This dualbenefit was a surprising, unexpected result from changing the shapes ofthe motive outlet and the discharge inlet that defines the Venturi gapand using an internal passageway that changes/taper according to ahyperbolic function.

One advantage of the aspirators disclosed herein is that a decreasedamount of engine air is consumed/needed to generate the vacuum necessaryto run a device requiring vacuum, which improves engine performancecompared to that obtained with a vacuum pump or an aspirator with aninternal circular profile.

Although the invention is shown and described with respect to certainembodiments, it is obvious that modifications will occur to thoseskilled in the art upon reading and understanding the specification, andthe present invention includes all such modifications.

What is claimed is:
 1. A Venturi device for producing vacuum from fluidsin an engine system comprising: a body defining a Venturi gap separatingapart an outlet end of a converging motive section and an inlet end of adiverging discharge section by a lineal distance, wherein the convergingmotive section and the diverging discharge section both gradually,continuously taper toward the Venturi gap; and a suction port in fluidcommunication with the Venturi gap; wherein the converging motivesection defines a circular-shaped motive inlet and an elliptical- orpolygonal-shaped motive outlet, the diverging discharge section definesan elliptical- or polygonal-shaped discharge inlet, and the convergingmotive section defines an inner passageway that transitions as ahyperbolic function from a motive inlet to the elliptical- orpolygonal-shaped motive outlet.
 2. The Venturi device of claim 1,wherein the diverging discharge section further defines acircular-shaped discharge outlet.
 3. The Venturi device of claim 1,wherein the suction port extends downward around the sides of the outletend of the converging motive section and the sides of the inlet end ofthe diverging discharge section and defines a void between all sidesthereof; and wherein the exterior profile of the outlet end of theconverging motive section and the inlet end of the diverging dischargesection generally match their respective internal shapes.
 4. The Venturidevice of claim 3, wherein the inlet end of the diverging dischargesection terminates with a rounded chamfer directing fluid flow into theelliptical- or polygonal-shaped discharge inlet.
 5. The Venturi deviceof claim 1, wherein the elliptical- or polygonal-shaped motive outlethas an eccentricity of 0.4 to 0.97.
 6. The Venturi device of claim 1,wherein the elliptical- or polygonal-shaped motive outlet has a ratio ofa major axis to a minor axis of about 2 to about 4, and the elliptical-or polygonal-shaped discharge inlet is offset, relative to theelliptical- or polygonal-shaped motive outlet, by the ratio of thedifference of the discharge inlet area and the motive outlet area to thepeak motive flow rate ((discharge inlet area−motive outlet area)/peakmotive flow rate) times a constant is greater than 0.28, wherein theconstant is equal to the speed of sound times the density of the fluidat the motive outlet.
 7. The Venturi device of claim 1, wherein theVenturi gap is proportional to the (motive mass flow rate)^(n), whereinn is 0.25 to 0.8.
 8. The Venturi device of claim 1, wherein the Venturigap is proportional to the (motive mass flow rate)^(n), wherein n is 0.4to 0.6.
 9. The Venturi device of claim 8, wherein the elliptical- orpolygonal-shaped motive outlet has an eccentricity of between 0 to, andincluding
 1. 10. The Venturi device of claim 1, wherein the offsetbetween the motive outlet and the discharge inlet is proportional to the(motive mass flow rate)^(n), wherein n is 0.25 to 0.8.
 11. The Venturidevice of claim 1, wherein the offset between the motive outlet and thedischarge inlet is proportional to the (motive mass flow rate)^(n),wherein n is 0.4 to 0.6.
 12. The Venturi device of claim 1, wherein aratio of suction inlet area/suction outlet area is between 3 and 12, theratio of motive inlet area/motive outlet area is greater than 4, and aratio of discharge outlet area/discharge inlet area is greater than 4.13. The Venturi device of claim 1, wherein the body further comprises abypass port intersecting the diverging discharge section downstream ofthe discharge inlet.
 14. An engine system comprising: A source of fluidpressure; a device requiring vacuum; an engine and an engine component;and a Venturi device according to claim 1; wherein the Venturi devicehas the suction port in fluid communication with the device requiringvacuum, the motive inlet in fluid communication with the source of fluidpressure, and a discharge outlet in fluid communication with the engineor the engine component.
 15. The engine system of claim 15, wherein thedevice requiring vacuum is a brake boost device, positive crankcaseventilation device, or fuel purge device.
 16. The engine system of claim15, wherein the source of fluid pressure is in a range of 5 kPa to 60kPa.